What do fires and deep sounds have in common? Not much right now, but they might have a lot in the future.Two George Mason University students have designed a device that uses sound waves to put out fires, thus potentially eliminating the need for carrying around huge quantities of water and costly cleaning operations. Here’s how it works:

Seth Robertson and Viet Tran’s wave extinguisher is not something you see everyday (or any day, for that matter) – they managed to hit the right note to blow fires away using only amps, a speaker and a device they invented and call “collimater”. The key here is to find a frequency which blows the oxygen away, and sound in the 30 to 60 hertz range seems to do the trick. Why does this work?

Well, sound waves are pressure waves, and they can displace some of the oxygen as they travel through the air. At some frequencies, the oxygen is pushed out more effectively, basically separated from the fire. The pressure waves then goes back and forth, agitating the oxygen away from the fire, preventing it from reigniting.

Robertson and Tran are electrical and computer engineering majors, and they came up with this idea for their project because they disliked all the ideas that came from their professors. Naturally, there were many naysayers. Most professors refused to serve as their advisors. Both colleagues and professors seemed extremely skeptical and advised them to pick something else, but they persevered, and ultimately Brian Mark agreed to oversee it. But even he was not convinced at first…

“My initial impression was that it wouldn’t work,” Mark, their adviser, said. “Some students take the safe path, but Viet and Seth took the higher-risk option.”

George Mason University.

 

Their first design didn’t work at all – they used very high frequencies of 30,000 hertz, but even though the flames danced, they never went out. But as they moved to lower frequencies, everything smoothened out.

“I honestly didn’t think it would work as well as it did,” Tran said.

Of course, they started out small and for now, their device can only put out small fires, but there is no reason why they shouldn’t scale it. For now, they want to test it more and see if the required frequency differs for some materials – but for starters, the advantages are obvious. Sure, you need some source of energy to use it, but that’s much easier to carry than huge quantities of water or powder – and then you don’t have any cleaning to do. To make things even better, this could actually work in space – where putting out a fire is actually really hard.

“In space, extinguisher contents spread all over. But you can direct sound waves without gravity,” explains Robertson.

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